Intelligent Amplifier Activation

1. A first playback device comprising: a physical control interface comprising a control that initiates rendering of media content by the first playback device; a proximity sensor arranged to detect movement in proximity to the physical control interface; an amplifier; a network interface; one or more processors; and a computer readable medium having stored thereon instructions executable by the one or more processors to cause the first playback device to perform functions comprising: while the amplifier of the first playback device is in an inactive state, detecting by the proximity sensor, movement in relation to the physical control interface of the first playback device; responsive to detecting the movement, causing the amplifier of the first playback device to enter an active state such that the amplifier is configured to produce amplified audio signals and sending, via the network interface, a message that causes an amplifier of a second playback device to enter the active state; receiving a user input to cause the first playback device to render media content; and responsive to receiving the user input, causing the first playback device to render media content in synchrony with the second playback device.

2. The first playback device of claim 1 , wherein receiving the user input to cause the first playback device to render media content comprises detecting a selection of the control that initiates rendering of media content by the first playback device.

3. The first playback device of claim 2 , wherein causing the first playback device to render media content comprises causing the first playback device to resume playing media that was paused.

4. The first playback device of claim 1 , wherein receiving the user input to cause the first playback device to render media content comprises receiving, from a control device, a message instructing the first playback device to render media content.

5. The first playback device of claim 4 , wherein causing the first playback device to render media content comprises causing the first playback device to render media content from a queue that is associated with the first playback device.

6. The first playback device of claim 1 , wherein the first playback device is a member of a first zone; and wherein the second playback device is a member of a second zone, and wherein causing the first playback device to render media content in synchrony with the second playback device comprises causing a zone group that includes the first zone and the second zone to render media content in synchrony.

7. The first playback device of claim 1 , wherein the first playback device is a first channel of a bonded stereo pair and the second playback device is a second channel of the bonded stereo pair; and wherein causing the first playback device to render media content in synchrony with the second playback device comprises causing the bonded stereo pair to render media content in synchrony.

8. The first playback device of claim 1 , wherein detecting by the proximity sensor, movement in relation to the physical control interface of the first playback device comprises detecting first movement within a first range of distances in relation to the first playback device, and wherein the functions further comprise: detecting, by the proximity sensor, second movement within a second range of distances; responsive to detecting the second movement, retrieving media content from a network audio source; and storing at least a portion of retrieved media content in a data storage medium of the first playback device.

9. The first playback device of claim 8 , wherein the second range of distances is nearer to the first playback device than the first range of distances.

10. The first playback device of claim 8 , wherein the functions further comprise: causing the second playback device to store at least the portion of retrieved media content in a data storage medium of the second playback device.

11. A tangible non-transitory computer-readable medium having stored thereon instructions executable by one or more processors to cause a first playback device to perform functions comprising: while an amplifier of the first playback device is in an inactive state, detecting by a proximity sensor of the first playback device, movement in relation to a physical control interface of the first playback device; responsive to detecting the movement, causing the amplifier of the first playback device to enter an active state such that the amplifier is configured to produce amplified audio signals and sending, via a network interface, a message that causes an amplifier of a second playback device to enter the active state; receiving a user input to cause the first playback device to render media content; and responsive to receiving the user input, causing the first playback device to render media content in synchrony with the second playback device.

12. The non-transitory computer-readable medium of claim 11 , wherein receiving the user input to cause the first playback device to render media content comprises detecting a selection of a control that initiates rendering of media content by the first playback device.

13. The non-transitory computer-readable medium of claim 11 , wherein receiving the user input to cause the first playback device to render media content comprises receiving, from a control device, a message instructing the first playback device to render media content.

14. The non-transitory computer-readable medium of claim 13 , wherein causing the first playback device to render media content comprises causing the first playback device to render media content from a queue that is associated with the first playback device.

15. The non-transitory computer-readable medium of claim 11 , wherein the first playback device is a member of a first zone; and wherein the second playback device is a member of a second zone, and wherein causing the first playback device to render media content in synchrony with the second playback device comprises causing a zone group that includes the first zone and the second zone to render media content in synchrony.

16. The non-transitory computer-readable medium of claim 11 , wherein the first playback device is a first channel of a bonded stereo pair and the second playback device is a second channel of the bonded stereo pair; and wherein causing the first playback device to render media content in synchrony with the second playback device comprises causing the bonded stereo pair to render media content in synchrony.

17. The non-transitory computer-readable medium of claim 11 , wherein detecting by the proximity sensor, movement in relation to the physical control interface of the first playback device comprises detecting first movement within a first range of distances in relation to the first playback device, and wherein the functions further comprise: detecting, by the proximity sensor, second movement within a second range of distances; responsive to detecting the second movement, retrieving media content from a network audio source; and storing at least a portion of retrieved media content in a data storage medium of the first playback device.

18. The non-transitory computer-readable medium of claim 17 , wherein the second range of distances is nearer to the first playback device than the first range of distances.

19. The non-transitory computer-readable medium of claim 17 , wherein the functions further comprise: causing the second playback device to store at least the portion of retrieved media content in a data storage medium of the second playback device.

20. A method comprising: while an amplifier of a first playback device is in an inactive state, detecting by a proximity sensor of the first playback device, movement in relation to a physical control interface of the first playback device; responsive to detecting the movement, causing the amplifier of the first playback device to enter an active state such that the amplifier is configured to produce amplified audio signals and sending, via a network interface, a message that causes an amplifier of a second playback device to enter the active state; receiving a user input to cause the first playback device to render media content; and responsive to receiving the user input, causing the first playback device to render media content in synchrony with the second playback device.